Lymphatic research represents an explosive field of new discovery in recent years. The cornea provides an ideal tissue for lymphatic studies due to its accessible location, transparent nature, and lymphatic-free and - inducible features. Additionally, corneal transplantation offers an excellent model for lymphatic research because it allows for (i) functional lymphatic cell trafficking studies; and (ii) the identification of cellulr contributions (donor or recipient source) to the process of lymphangiogenesis (LG). Studies on corneal LG bears direct implication to high-risk (HR) transplantation where grafting is performed on lymphatic-rich host beds and the rejection rate can be as high as 90%. Many patients who are blind from corneal diseases fall into this category after inflammatory, infectious, traumatic, r chemical insults. To date, there is no effective management for this situation. Our long-term goal is to elucidate the molecular and cellular mechanisms of LG using both in vitro cell culture and in vivo corneal models, a necessary prerequisite to the development of new therapeutic protocols. Our hypothesis is that corneal LG can be manipulated through specific lymphatic factors or cell populations. Molecular blockade of the lymphatic factors promotes HR graft survival. This proposal is based on the most recent advances in technology and lymphatic research, and a large amount of preliminary data we have generated during the past few years. The specific aims are: 1) define the role of integrin alpha 9 (Itga-9) in corneal lymphatic valve formation and function using neutralizing antibodies and knockout mice; 2) determine the role of Angiopoietin-2 (Ang-2) in lymphatic endothelial cell functions in vitro, and LG and transplant rejection in vivo using small interference RNAs, neutralizing antibodies, and knockout mice; and 3) investigate the cell origins of lymphatic vessels using cell type-specific gene-manipulated mice and live imaging techniques. Research on corneal LG will have broader clinical implications beyond the treatment of ocular diseases alone since lymphatic dysfunction is associated with a diverse array of diseases and conditions, which include but are not limited to cancer metastasis, inflammation, infections, diabetes, obesity, hypertension and lymphedema.